Norm Peterson
corner barstool sitter
Virtually all of the online wheel revs/mile and speeds in gears calculators ignore the fact that tire treads compress slightly in the circumferential direction as they roll through contact with the ground. So they end up turning a few more times in a mile than what the math based only on tire dimensions predicts.
3% is a reasonable correction in most cases, though this tread compliance correction for a few tires is slightly less (~1.5% - 2%).
So if you were to calculate a tire as being 750 revs/mile, you're probably going to see mfr-tabulated numbers more like 770 or a bit more. Trust either the mfr or this correction.
The online calculators really are well-intentioned, and since this effect is not exactly common knowledge among enthusiasts I'm not blaming anybody for making this oversight.
Norm
3% is a reasonable correction in most cases, though this tread compliance correction for a few tires is slightly less (~1.5% - 2%).
So if you were to calculate a tire as being 750 revs/mile, you're probably going to see mfr-tabulated numbers more like 770 or a bit more. Trust either the mfr or this correction.
The online calculators really are well-intentioned, and since this effect is not exactly common knowledge among enthusiasts I'm not blaming anybody for making this oversight.
Norm
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